如下
-- 表结构
-- stops(id, name)
-- route(num,company,pos, stop)
-- 列出巴士公司'LRT'的'4'号巴士线的站编号id 和 站名name
SELECT s.id,s.name FROM stops s JOIN route r ON(r.stop=s.id) WHERE r.company = 'LRT' AND num = 4;
-- OR
SELECT s.id,s.name FROM stops s, route r WHERE r.stop=s.id AND r.company = 'LRT' AND num = 4;
-- OR
SELECT s.id,s.name FROM stops s WHERE s.id IN (SELECT stop FROM route r WHERE r.company = 'LRT' AND num = 4);
三个语句的结果是相同的,但是想知道效率方面哪个好一些